In the art, elastomeric compositions are known, which contain polymers functionalized with reactive groups, which are fluids under ambient conditions, and are capable of crosslinking, due to the effect of atmosphere humidity, into solid and rubbery products, endowed with characteristics which make them useful in sealant compositions.
U.K. Pat. No. 1,167,521 discloses a process for transforming polymers of hydrocarbon type, e.g., copolymers of isobutene with piperylene, into polymers crosslinking under the influence of the ambient humidity, by means of the grafting of a chlorosilane in the presence of catalysts.
The disadvantage of the process consists in the severe grafting conditions: in fact, excess amounts of chlorosilane and free-radical catalysis are used, in as much as the milder catalysts based on platinum have resulted inefficacious.
In Polymer Sci. Polymer Chem., 18th Ed., 1529 (1980) and Polym. Bull. 1 575, (1979), Kennedy describes the preparation of .alpha.,.omega.-chlorosilane-derivatives of polyisobutenes, followed by the treatment with alcohols, to yield polymers containing the alkoxysilanic function, crosslinkable in the presence of ambient humidity.
Such preparation is anyway difficultly applicable on an industrial scale, due to the complexity and of the high costs thereof.
In U.S. Pat. No. 4,524,187, issued on June 18, 1985, a process is disclosed for preparing fluid silylated copolymers of isobutene, suitable for use in sealants, and crosslinkable under the influence of the ambient humidity. According to this process, particular copolymers of isobutene with 1,3,7-octatriene or with 5-methyl-1,3,6-heptatriene are grafted with chlorosilanes, such as, e.g., HSiMeCl.sub.2 and HSiMe.sub.2 Cl. The alkoxysilanic functions necessary for the crosslinking are obtained by means of the subsequent treatment with alcohols. In this process, mild grafting conditions in the presence of platinum-based catalysts, or the like, are used. In U.S. Pat. No. 4,524,187 issued on June 18, 1985 the alkoxysilanic function is on the contrary directly grafted on copolymers of isobutene with 1,3,7-octatriene or 5-methyl-1,3,6-heptatriene, by means of the reaction with thiomercaptopropylalkoxysilanes in the presence of free-radical or anionic catalysts.
The processes disclosed in said U.S. Patent is burdensome and shows the drawback that the special copolymers of isobutene with 1,3,7-octatriene or 5-methyl-1,3,6-heptatriene must be produced according to a process wherein blends of (chlorinated/non-chlorinated) solvents are used, to secure the solubility of the catalyst, with this latter being furthermore used in large amounts, and that in the subsequent grafting reaction the solvent must be changed.